Multi-parameter isolators are often equipped with damper assemblies, which include opposing hydraulic chambers containing a damping fluid. As the operative temperature of the multi-parameter isolator changes, so too does the volume of the damping fluid contained within the damper assembly; the term “operative temperature,” as appearing herein, denoting the temperature of the damping fluid or, more generally, the isolator when deployed in field and not necessarily when the isolator is active. In instances wherein the multi-parameter isolator is exposed to significant temperature changes, as may occur when the isolator is included within a spacecraft isolation system or deployed onboard a high altitude airborne platform, relatively pronounced fluctuations in damping fluid volume may occur. Under high temperature operating conditions, the pressure within the hydraulic chambers of the damper assembly may become undesirably high if accommodations are not provided for damping fluid expansion. Such undesirably high pressures may result in buckling of any internally-pressurized bellows included within the damper assembly, undesirably high mechanical stress applied to the bellows and other damper assembly components, and potential leakage of the damping fluid. Conversely, under low temperature operating conditions, the pressure within the damper assembly may become undesirably depressed and cavitation may occur if means are not provided to compensate for the decrease in damping fluid volume.
To help regulate the fluid pressure within a damper assembly and thereby mitigate the above-described issues, multi-parameter isolators subject to broad operative temperature ranges are often further equipped with a thermal compensation device or, more simply, a Thermal Compensator (“TC”). By common design, a TC includes a variable-volume chamber, which is fluidly coupled to the hydraulic chambers of the damper assembly. The variable-volume chamber may be defined, in part, by a TC piston and a TC bellows, which is sealingly joined to the TC piston. The bellows is inherently resilient and urges the TC piston toward an extended position corresponding to the free length position of the bellows. In some implementations, a coil spring may also be provided to exert an additional preload force urging the TC piston toward the extended position. As the pressure of the damping fluid within the damper assembly increases, the force exerted on the face of the TC piston by the damping fluid eventually exceeds the bias force of the bellows and the TC preload spring (if provided). In response, the TC piston moves toward a retracted position, and the bellows compresses. This results in an increase in the volume of the TC chamber to help offset the damping fluid expansion and maintain the damping fluid pressure below a maximum threshold value. Conversely, when the pressure within the damper assembly decreases, the force exerted on the TC piston by the damping fluid is eventually surpassed by the bias force exerted on the piston by the TC bellows and the TC preload spring. The TC piston thus moves toward its extended position, and the bellows expands. This reduces the volume of the TC chamber to partially compensate for the decrease in damping fluid volume and preventing the damping fluid pressure from falling below above below a minimum threshold value.